﻿namespace WPJFlacLib.JFlac.Util
{
    internal class CRC8
    {
        private static readonly byte[] CRC8_TABLE =
            new byte[]
                {
                    0x00,
                    0x07,
                    0x0E,
                    0x09,
                    0x1C,
                    0x1B,
                    0x12,
                    0x15,
                    0x38,
                    0x3F,
                    0x36,
                    0x31,
                    0x24,
                    0x23,
                    0x2A,
                    0x2D,
                    0x70,
                    0x77,
                    0x7E,
                    0x79,
                    0x6C,
                    0x6B,
                    0x62,
                    0x65,
                    0x48,
                    0x4F,
                    0x46,
                    0x41,
                    0x54,
                    0x53,
                    0x5A,
                    0x5D,
                    0xE0,
                    0xE7,
                    0xEE,
                    0xE9,
                    0xFC,
                    0xFB,
                    0xF2,
                    0xF5,
                    0xD8,
                    0xDF,
                    0xD6,
                    0xD1,
                    0xC4,
                    0xC3,
                    0xCA,
                    0xCD,
                    0x90,
                    0x97,
                    0x9E,
                    0x99,
                    0x8C,
                    0x8B,
                    0x82,
                    0x85,
                    0xA8,
                    0xAF,
                    0xA6,
                    0xA1,
                    0xB4,
                    0xB3,
                    0xBA,
                    0xBD,
                    0xC7,
                    0xC0,
                    0xC9,
                    0xCE,
                    0xDB,
                    0xDC,
                    0xD5,
                    0xD2,
                    0xFF,
                    0xF8,
                    0xF1,
                    0xF6,
                    0xE3,
                    0xE4,
                    0xED,
                    0xEA,
                    0xB7,
                    0xB0,
                    0xB9,
                    0xBE,
                    0xAB,
                    0xAC,
                    0xA5,
                    0xA2,
                    0x8F,
                    0x88,
                    0x81,
                    0x86,
                    0x93,
                    0x94,
                    0x9D,
                    0x9A,
                    0x27,
                    0x20,
                    0x29,
                    0x2E,
                    0x3B,
                    0x3C,
                    0x35,
                    0x32,
                    0x1F,
                    0x18,
                    0x11,
                    0x16,
                    0x03,
                    0x04,
                    0x0D,
                    0x0A,
                    0x57,
                    0x50,
                    0x59,
                    0x5E,
                    0x4B,
                    0x4C,
                    0x45,
                    0x42,
                    0x6F,
                    0x68,
                    0x61,
                    0x66,
                    0x73,
                    0x74,
                    0x7D,
                    0x7A,
                    0x89,
                    0x8E,
                    0x87,
                    0x80,
                    0x95,
                    0x92,
                    0x9B,
                    0x9C,
                    0xB1,
                    0xB6,
                    0xBF,
                    0xB8,
                    0xAD,
                    0xAA,
                    0xA3,
                    0xA4,
                    0xF9,
                    0xFE,
                    0xF7,
                    0xF0,
                    0xE5,
                    0xE2,
                    0xEB,
                    0xEC,
                    0xC1,
                    0xC6,
                    0xCF,
                    0xC8,
                    0xDD,
                    0xDA,
                    0xD3,
                    0xD4,
                    0x69,
                    0x6E,
                    0x67,
                    0x60,
                    0x75,
                    0x72,
                    0x7B,
                    0x7C,
                    0x51,
                    0x56,
                    0x5F,
                    0x58,
                    0x4D,
                    0x4A,
                    0x43,
                    0x44,
                    0x19,
                    0x1E,
                    0x17,
                    0x10,
                    0x05,
                    0x02,
                    0x0B,
                    0x0C,
                    0x21,
                    0x26,
                    0x2F,
                    0x28,
                    0x3D,
                    0x3A,
                    0x33,
                    0x34,
                    0x4E,
                    0x49,
                    0x40,
                    0x47,
                    0x52,
                    0x55,
                    0x5C,
                    0x5B,
                    0x76,
                    0x71,
                    0x78,
                    0x7F,
                    0x6A,
                    0x6D,
                    0x64,
                    0x63,
                    0x3E,
                    0x39,
                    0x30,
                    0x37,
                    0x22,
                    0x25,
                    0x2C,
                    0x2B,
                    0x06,
                    0x01,
                    0x08,
                    0x0F,
                    0x1A,
                    0x1D,
                    0x14,
                    0x13,
                    0xAE,
                    0xA9,
                    0xA0,
                    0xA7,
                    0xB2,
                    0xB5,
                    0xBC,
                    0xBB,
                    0x96,
                    0x91,
                    0x98,
                    0x9F,
                    0x8A,
                    0x8D,
                    0x84,
                    0x83,
                    0xDE,
                    0xD9,
                    0xD0,
                    0xD7,
                    0xC2,
                    0xC5,
                    0xCC,
                    0xCB,
                    0xE6,
                    0xE1,
                    0xE8,
                    0xEF,
                    0xFA,
                    0xFD,
                    0xF4,
                    0xF3
                };

        /**
     * Update the CRC value with a byte data.
     * 
     * @param data  The byte data
     * @param crc   The starting CRC value
     * @return      The updated CRC value
     */

        public static byte Update(byte data, byte crc)
        {
            return CRC8_TABLE[crc ^ data];
        }

        /**
     * Update the CRC value with data from a byte array.
     * 
     * @param data  The byte array
     * @param len   The byte array length
     * @param crc   The starting CRC value
     * @return      The updated CRC value
     */

        public static byte UpdateBlock(byte[] data, int len, byte crc)
        {
            for (int i = 0; i < len; i++)
                crc = CRC8_TABLE[crc ^ data[i]];
            return crc;
        }

        /**
     * Calculate the CRC value with data from a byte array.
     * 
     * @param data  The byte array
     * @param len   The byte array length
     * @return      The calculated CRC value
     */

        public static byte Calc(byte[] data, int len)
        {
            byte crc = 0;

            for (int i = 0; i < len; i++)
                crc = CRC8_TABLE[(crc ^ data[i]) & 0xff];

            return crc;
        }
    }
}